<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>

        * {
            margin:0px;padding:0px;
        }

        body {
            margin: 50px;
        }

        .box {
            width:100%;
            height:100vh;
            display:flex;
        }
        .left {
            flex:1;
            background:blue;
        }
        .center {
            flex:1;
            background:red;
            margin:0 10px;
        }
        .right {
            flex:1;
            background:black;
        }

    </style>
</head>
<body>
<div class="box">
    <div class="left"></div>
    <div class="center"></div>
    <div class="right"></div>
</div>
</body>
</html>